Rc

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rc is the command line interpreter for Version 10 Unix and Plan 9 from Bell Labs operating systems. It resembles the Bourne shell, but its syntax is somewhat simpler. It was created by Tom Duff, who is better known for an unusual C programming language construct called Duff's device.

A port of the original rc to Unix is part of Plan 9 from User Space. A rewrite of rc for Unix-like operating systems by Byron Rakitzis is also available but includes some incompatible changes.

Rc uses C-like control structures instead of ALGOL-like, as the original Bourne shell uses, except that it uses a construct if not instead of else and has a Bourne-like for loop to iterate over lists. In rc all variables are lists of strings, which eliminates the need for constructs like "$@".

Examples

For example, the Bourne shell script

if test $1 = hello; then
    echo hello, world
else
    case $2 in
    1) echo $# 'hey' "jude's"$3;;
    2) echo `date` :$*: :"$@":;;
    *) echo why not 1>&2
    esac
    for i in a b c; do
        echo $i
    done
fi

is expressed in rc as

if(~ $1 hello)
    echo hello, world
if not {
    switch($2) {
    case 1
        echo $#* 'hey' 'jude''s'^$3
    case 2
        echo `{date} :$"*: :$*:
    case *
        echo why not >[1=2]
    }
    for(i in a b c)
        echo $i
}

Because if and if not are two different statements, they must be grouped in order to be used in certain situations.

Rc also supports more dynamic piping:

a |[2] b    # pipe standard error of a to b — in Bourne shell as a 1>&2 | b
a <>b       # opens b as a's standard input and standard output
a <{b} <{c} # becomes a {standard output of b} {standard output of c}

References

External links

• "Rc - The Plan 9 Shell" - by Tom Duff
• Plan 9 rc manual page
• Plan 9 from User Space - Includes rc and other Plan 9 tools for Linux, Mac OS X and other Unix-like systems.
• Byron Rakitzis' rewrite for Unix
• werc - A web document management system implemented completely in the rc shell.

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